The proposed training program is a continuation of one in force since 1986 at the Whitehead Institute for Biomedical Research. The Whitehead Institute is a free-standing research institute having close ties with the Biology Department of the Massachusetts Institute of Technology (MIT). The program, as proposed, will support the research training of 8 pre-doctoral students working on cellular growth control and allied research areas. A number of the mechanisms involved in cell growth control suffer disruption during the development of tumors, leading in turn to the deregulated proliferation of cancer cells. The students to be trained will first be admitted to the doctoral program of the Graduate Department of Biology of MIT. After one year of formal classroom training in the MIT Graduate Biology Program, they will begin their laboratory research work at the Whitehead Institute and will complete the requirements for their doctoral degree while at the Whitehead Institute. The proposed training program includes a number of components in addition to the laboratory research required for the doctoral thesis. Included are weekly group and inter-group meetings and attendance at a wide range of public seminars and lectures. Trainees will have frequent contacts with pre- and post-doctoral researchers in both their own laboratories and in those of allied laboratories at the Whitehead Institute and the MIT Department of Biology. A unique aspect of the proposed training program is the emphasis placed on strong, ongoing interactions with scientists outside the trainees' own research groups, enabling them to benefit from the expertise developed in the various research groups at the Whitehead Institute and the large MIT community of biologists.